Hosts, such as computers, personal digital assistants (PDAs) and other network enabled devices, typically communicate with other link partners over a medium. The medium may be a fiber-optic cable or copper cable. Referring now to FIG. 1A, a first network device 10-1 includes a medium access control (MAC) device 16-1 and a physical layer (PHY) device 20-1. The MAC and PHY devices 16-1 and 20-1, respectively, may communicate using a media independent interface (MII). A transmit path of the PHY device 20-1 includes a physical coding sublayer (PCS) device 22-1. A second network device 10-2 or link partner includes similar components that are labeled with the same reference number having an “−2” extension in FIG. 1A. A medium 24 connects the first and second network devices 10-1 and 10-2.
Referring now to FIG. 1B, the PCS devices 22-1 and 22-2 (collectively PCS devices 22) for 100BASE-X are shown. The PCS devices 22 include a converter module 26 that converts 4 input bits to 5 output bits. A scrambler module 28 selectively performs scrambling for 100BASE-TX according to a scrambling algorithm and not for 100BASE-FX. An encoding module 30 performs encoding such as multi-level 3 (MLT3) modulation for 100BASE-TX and non return to zero inverted (NRZI) modulation for 100BASE-FX.